One of the major objects in treatment of head and neck cancer is a suppression of lymph node metastasis. As such cervical lymph node metastasis and the number of metastasized lymph nodes impose a great influence on prognosis of a patient, ascertainment of the aspect of metastasis of the cervical lymph node is necessary and indispensable for treatment. However, there is a limitation in detection of potential lymph node metastasis (smaller than about 5 mm) by the methods such as palpation and imaging diagnoses (CT, MRI, Echo, PET-CT). For a further accurate diagnosis of lymph node metastasis, a sentinel lymph node biopsy has been conducted (Non-patent documents 1-3). The sentinel lymph node biopsy has been applied clinically to various carcinomas after Morton et al. reported a usefulness of the sentinel lymph node against malignant melanoma in 1992 (Non-patent document 4), and the usefulness to the head and neck cancer also has already been reported (Non-patent documents 2 and 3).
Historical studies regarding diagnosis of lymph node micrometastasis have clarified that presence of a metastatic focus having a maximal diameter of 200 μm or more can be found with HE stain, that even a fewer tumor cells can be discovered by a concurrent use of cytokeratin immunostaining, and that one or several tumor cells can be detected in a genetic diagnosis by a realtime quantitative RT-PCR method where Squamous Cell Carcinoma Antigen (SCCA) gene is effective as the target gene for detection (Non-patent documents 5-8). Further, it has been disclosed that the lymph node metastasis of head and neck squamous cell carcinoma can be diagnosed by use of QRT-PCR method on the basis of the expression level of PVA (pemphigus vulgaris antigen) gene (Non-patent document 9).
Furthermore, for tumor markers for head and neck cancer, several genes have been disclosed (Patent documents 1 and 2).